US6005635A - Displaying aliased and anti-aliased characters from a source font - Google Patents
Displaying aliased and anti-aliased characters from a source font Download PDFInfo
- Publication number
- US6005635A US6005635A US08/858,012 US85801297A US6005635A US 6005635 A US6005635 A US 6005635A US 85801297 A US85801297 A US 85801297A US 6005635 A US6005635 A US 6005635A
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- look
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- 238000000034 method Methods 0.000 claims abstract description 27
- 230000001419 dependent effect Effects 0.000 claims 1
- 230000000694 effects Effects 0.000 abstract description 7
- 230000007704 transition Effects 0.000 abstract description 2
- 230000008569 process Effects 0.000 description 10
- 239000003086 colorant Substances 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 239000004973 liquid crystal related substance Substances 0.000 description 1
- 230000008447 perception Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
- G09G5/22—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the display of characters or indicia using display control signals derived from coded signals representing the characters or indicia, e.g. with a character-code memory
- G09G5/24—Generation of individual character patterns
- G09G5/28—Generation of individual character patterns for enhancement of character form, e.g. smoothing
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
- G09G5/02—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed
- G09G5/026—Control of mixing and/or overlay of colours in general
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
- G09G5/02—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed
- G09G5/06—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed using colour palettes, e.g. look-up tables
Definitions
- the present invention is related to the storage and generation of displayable character fonts in aliased and anti-aliased form.
- a display screen composed of discrete display points or pixels will generally not be able to display a diagonal line without producing a jagged line which has a "staircase" appearance. Since the jagged appearance is undesirable, a variety of anti-aliasing techniques are used to visibly minimize the aliased effects.
- the system and method of the present invention provide a simple, but effective, technique for generating aliased and anti-aliased images such as fonts, while minimizing both processor and memory requirements.
- a source pixel representation of the character is stored in memory.
- the source pixel representations are generated by dividing the pixels of each anti-aliased character among at least three non-overlapping regions which provide a color/intensity transition between the character and the background to produce an anti-aliased effect.
- three regions are defined. The regions are identified as the foreground region, middle region and background region.
- the source pixel representation of the character described by the three regions is referenced from memory. If the character is to be aliased the middle and background regions are coded to the background color and the foreground region is coded to the foreground color of the character. If the character is to be anti-aliased, the foreground, middle and background regions are coded, respectively, to the color of the character, a value to provide an anti-aliased effect, and the background color.
- FIG. 1 illustrates a satellite receiver system employing an embodiment of the present invention
- FIG. 2 illustrates a receiver including a character generation device employing the present invention
- FIG. 3 illustrates an italicized character "I" with pixels divided among three color code regions
- FIG. 4 is a flow diagram illustrating an aliased and anti-aliased image generation routine according to one embodiment
- FIG. 5 is a flow diagram illustrating an aliased and anti-aliased image generation routine according to an alternate embodiment
- FIG. 6 is a flow diagram illustrating an aliased and anti-aliased image generation routine according to an alternate embodiment.
- FIG. 7 is a character generation device according to one embodiment employing multiple windows and multiple color look-up tables.
- a method and apparatus for using one source font to display both aliased and anti-aliased images is described. Although described with reference to certain specific embodiments, those skilled in the art will recognize that the present invention may be practiced without some or all of these details and, further, that the invention may be used in systems (such as wordprocessing or user interfaces) other than the home satellite television receiving system discussed below. More specifically, although the description is made in the context of alphanumeric characters it is clear that the teaching of the invention is generally applicable to a large number of different types of image objects.
- the present invention decreases the memory and computational intensity requirements of a system that displays both aliased and anti-aliased images. In particular, a system does not have to store two versions, aliased and anti-aliased, of each font.
- a system storing only an aliased version does not have to calculate "on the fly" the anti-aliased version.
- a source pixel representation typically an anti-aliased version of the font, is used to display both aliased and anti-aliased characters.
- FIG. 1 illustrates a satellite receiver system 10 employing an embodiment of the present invention.
- Satellite receiver system 10 includes an antenna 12 coupled to a receiver 14. Antenna 12 is to be aligned so as to receive a signal broadcast by a satellite. Signals received by antenna 12 are amplified and downconverted prior to transmission to receiver 14. Such signals generally include audio and/or video information which is decoded by receiver 14. The decoded audio and/or video information is then presented by the receiver 14 to the television (TV) 16 for display.
- the video information may contain broadcasts of programming as well as instructions to display textual messages or images, on the TV 16. These messages may form an electronic program guide of program descriptions or some other information to the user.
- the TV 16 is a cathode ray tube (CRT) but those skilled in the art understand it can also be a liquid crystal display.
- CTR cathode ray tube
- receiver 14 includes a character generation device 20 and a receiver subsystem 28.
- the character generation device 20 includes a memory device 22, a central processing unit (CPU) 24, and a color generator 26.
- CPU central processing unit
- the receiver subsystem 28 decodes video instructions received through satellite signals and transmits them to the CPU 24 to display text and other images on the TV 16.
- the memory 22 is configured to store instructions executed by the CPU 24 to perform functions, such as those described herein, and source pixel representations of images and fonts.
- the system described uses a processor and memory, those skilled in the art understand that the present invention may be implemented using hardware exclusively or a mixture of software and hardware.
- the CPU may be implemented using control logic or circuitry, an embedded controller or other logic devices that can implement a state machine.
- the memory 22 is read only memory (ROM).
- ROM read only memory
- random access memory e.g., static RAM, dynamic RAM
- a mixture of ROM and RAM can also be used for the memory 22.
- the color generator 26 can be implemented using programmable logic, RAM or ROM.
- the color generator is a color look-up table 26 implemented as RAM.
- the CPU 24 inputs the pixel values into the color look-up table 26.
- the color look-up table 26 generates color codes for the regions of a source pixel representation.
- FIG. 3a A source pixel representation of one character of a font in accordance with one embodiment of the present invention is illustrated in FIG. 3a.
- the source pixel representation has multiple pixels that are divided among a foreground region, a middle region, and a background region.
- the pixel values in each region correspond to a different color.
- the CPU 24 retrieves the source pixel representations of the characters from memory 22.
- the pixel values retrieved from memory are then used to index into the the color look-up table (CLUT) 26.
- the CLUT 26 generates color codes for each pixel which a display controller (not shown) uses to display pixels which form the characters as aliased or anti-aliased images on TV 16 of FIG. 2.
- a foreground color output form the CLUT 26 is selected for the foreground region pixels and the middle region pixels and a background color is selected for the background region pixels.
- the technique for choosing the foreground colors and background colors displayed so as to achieve a desired degree of contrast between the foreground region pixels and the background region pixels is well known in the art and is not repeated here.
- a foreground color, a color to provide an anti-aliased effect, and a background color are generated, respectively, for the foreground, middle and background regions.
- the technique for choosing a foreground color, a color to provide an anti-aliased effect, and a background color so as to reduce a viewer's perception of aliasing is well known in the art and is not repeated here.
- FIG. 3b illustrates a source pixel representation of one character of a font in accordance with the preferred embodiment of the present invention.
- the source pixel representation has multiple pixels that are divided among a foreground region, a middle1 region, a middle2 region and a background region.
- the pixel values in each region correspond to a different color.
- a foreground color is selected for the foreground region pixels and the middle1 region pixels
- a background color is selected for the middle2 region pixels and the background region pixels.
- a foreground color is selected for the foreground region pixels
- a first intermediate color is selected for the middle1 region
- a second intermediate color is selected for the middle2 region
- a background color is selected for the background region.
- the first and second intermediate colors may be the same.
- characters are written to particular windows of the display.
- Each window corresponds to an area on the display screen in which video, text or other images are displayed.
- Each window has a color look-up table associated with it.
- the color codes are stored in a particular sequence in a CLUT to define whether the resultant image is aliased or anti-aliased. For example, the color codes indexed by pixel values in the foreground region and middle region correspond to each other in an aliased CLUT and the color codes indexed by the same pixel values in an anti-aliased CLUT are different.
- each CLUT of a plurality of CLUTS consistently renders aliased or anti-aliased images.
- each CLUT is associated with a particular window and is pre-configured to generate an aliased or anti-aliased image with certain fixed colors.
- the memory 22 contains multiple color look-up tables.
- CPU 24 accesses a particular color look-up table based in part upon whether the image is to be aliased or anti-aliased.
- FIGS. 4, 5 & 6 illustrate multiple processes that are utilized by alternative embodiments of the present invention.
- the embodiments described in FIGS. 4, 5 & 6 describe the process with respect to a three region character.
- the processes can be expanded to include representations having more than three regions.
- the processes can be configured to have the display output of pixels in one or more than one of the middle regions to correspond to the color of the foreground region and have the display output of pixels in the remaining middle regions to correspond to the color of the background region.
- the source pixel region includes two middle regions and the image is to be aliased
- the pixels of one middle region e.g., the one closest to the foreground region
- the pixels in the other middle region would be displayed as the background color.
- the processes described herein cover the pixels in the middle region to be displayed as the foreground color when the image is to be aliased.
- the processes could be configured to display the pixels in the middle region in the background color when the displayed image is to be aliased.
- FIG. 4 generally describes the process. Referring to FIG. 4, a source pixel representation of a character to be displayed is retrieved at step 104. At step 107, it is determined whether the character is to be rendered as an aliased or an anti-aliased image. If the character is to be aliased, then the process continues at step 108, where a foreground color code is generated for the pixels in both the foreground region and the middle region, and a background color code is generated for the pixels in the background region.
- step 110 a foreground color code is generated for the pixels in the foreground region, a middle color code is generated for the pixels in the middle region, and a background color code is generated for the pixels in the background region.
- FIG. 5 illustrates one embodiment of the present invention.
- general purpose color look-up tables not configured specifically for the generation of aliased or anti-aliased images are used.
- a source pixel representation of a character to be displayed is retrieved.
- a foreground color code used by the display controller is generated for the foreground region pixel values, and a background color code is generated for the background region pixel values. If the image is to be anti-aliased, the pixel values of the middle region are not set to correspond to the pixel values of the foreground region, and, therefore, at step 216, foreground color codes are generated for the foreground region pixel values, middle color codes are generated for the middle region pixel values, and background color codes are generated for the background region pixel values.
- the CLUT itself can be dynamically updated to change selected values in the CLUT to ensure the middle region pixel values will cause the CLUT to output the foreground color code when an aliased image is to be displayed.
- FIG. 6 illustrates an alternative process.
- an aliased CLUT and anti-aliased CLUT are provided.
- the aliased CLUT and anti-aliased CLUT are each respectively configured to cause the middle region pixel values to output a foreground region color code and a middle region color code.
- a source pixel representation of a character to be displayed is retrieved.
- the aliased CLUT is accessed and foreground color codes are generated for the pixels in the foreground region and the middle region, and background color codes are generated for the pixels in the background region.
- foreground color codes are generated for pixels in the foreground region
- middle color codes are generated for pixels in the middle region
- background color codes are generated for pixels in the background region.
- one embodiment of the present invention employs multiple color look-up tables 36, 38, 40, 42, 44, 46, 48, 50.
- Each of the multiple color look-up tables 36 is associated with a distinct and separate window.
- Each window is associated with an area of the physical display screen (not shown) and is characterized to display aliased and anti-aliased images.
- aliased or anti-aliased images may be displayed in the corresponding area of the physical display screen with minimal processing overhead.
- FIG. 7 illustrates separate color look-up tables
- color look-up tables can be implemented in a single memory device, multiple memory devices, a single logic device or multiple logic devices.
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- Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Controls And Circuits For Display Device (AREA)
- Studio Circuits (AREA)
Abstract
Description
Claims (22)
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/858,012 US6005635A (en) | 1997-05-16 | 1997-05-16 | Displaying aliased and anti-aliased characters from a source font |
JP13573498A JP4151807B2 (en) | 1997-05-16 | 1998-05-18 | Image generating method and character generating apparatus |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US08/858,012 US6005635A (en) | 1997-05-16 | 1997-05-16 | Displaying aliased and anti-aliased characters from a source font |
Publications (1)
Publication Number | Publication Date |
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US6005635A true US6005635A (en) | 1999-12-21 |
Family
ID=25327237
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US08/858,012 Expired - Lifetime US6005635A (en) | 1997-05-16 | 1997-05-16 | Displaying aliased and anti-aliased characters from a source font |
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US (1) | US6005635A (en) |
JP (1) | JP4151807B2 (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1026659A2 (en) * | 1999-02-01 | 2000-08-09 | Sharp Kabushiki Kaisha | Character display apparatus, character display method, and recording medium |
EP1111579A2 (en) * | 1999-12-24 | 2001-06-27 | Sharp Kabushiki Kaisha | Character display device, character display method, and recording medium therefor |
US20070109314A1 (en) * | 2003-05-23 | 2007-05-17 | Via Technologies, Inc. | Adaptive pixel-based blending method and system |
-
1997
- 1997-05-16 US US08/858,012 patent/US6005635A/en not_active Expired - Lifetime
-
1998
- 1998-05-18 JP JP13573498A patent/JP4151807B2/en not_active Expired - Fee Related
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP1026659A2 (en) * | 1999-02-01 | 2000-08-09 | Sharp Kabushiki Kaisha | Character display apparatus, character display method, and recording medium |
EP1026659A3 (en) * | 1999-02-01 | 2002-01-30 | Sharp Kabushiki Kaisha | Character display apparatus, character display method, and recording medium |
US6542161B1 (en) | 1999-02-01 | 2003-04-01 | Sharp Kabushiki Kaisha | Character display apparatus, character display method, and recording medium |
EP1111579A2 (en) * | 1999-12-24 | 2001-06-27 | Sharp Kabushiki Kaisha | Character display device, character display method, and recording medium therefor |
EP1111579A3 (en) * | 1999-12-24 | 2002-01-02 | Sharp Kabushiki Kaisha | Character display device, character display method, and recording medium therefor |
US6766052B2 (en) | 1999-12-24 | 2004-07-20 | Sharp Kabushiki Kaisha | Character display device, character display method, and recording medium therefor |
US20070109314A1 (en) * | 2003-05-23 | 2007-05-17 | Via Technologies, Inc. | Adaptive pixel-based blending method and system |
Also Published As
Publication number | Publication date |
---|---|
JPH1152939A (en) | 1999-02-26 |
JP4151807B2 (en) | 2008-09-17 |
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AS | Assignment |
Owner name: SONY CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SAIB, JOSEPH;SUZUKI, ATSUSHI;REEL/FRAME:008571/0689 Effective date: 19970513 Owner name: SONY ELECTRONICS, INC., NEW JERSEY Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SAIB, JOSEPH;SUZUKI, ATSUSHI;REEL/FRAME:008571/0689 Effective date: 19970513 |
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